Project 2 - Measuring distance of an object using ultrasonic sensor (HC-SR04)

Distance = Speed x Time

Hardware Requirements

• NodeMCU
• HC-SR04 (Ultra-sonic Sensor)
• Bread Board
• Jumper Wires
• Micro USB Cable

To measure the distance the sound has travelled we use the formula: Distance = (Time x SpeedOfSound) / 2. The "2" is in the formula because the sound has to travel back and forth. First the sound travels away from the sensor, and then it bounces off of a surface and returns back.

#define F_CPU 8000000UL
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <string.h>
#include <stdlib.h>

#define LCD_Data_Dir DDRD
#define LCD_Command_Dir DDRC
#define LCD_Data_Port PORTD
#define LCD_Command_Port PORTC
#define EN PC2
#define RW PC3
#define RS PC4

void LCD_Command (char);
void LCD_Char (char);
void LCD_Init (void);
void LCD_String (char*);
void LCD_String_xy (char,char,char*);

void LCD_Command (char cmd)
{
LCD_Data_Port = cmd;
LCD_Command_Port &= ~((1<<RS)|(1<<RW));
LCD_Command_Port |= (1<<EN);
_delay_us(1);
LCD_Command_Port &= ~(1<<EN);
_delay_ms(3);
}

void LCD_Char (char char_data)
{
LCD_Data_Port = char_data;
LCD_Command_Port &= ~(1<<RW);
LCD_Command_Port |= (1<<EN)|(1<<RS);
_delay_us(1);
LCD_Command_Port &= ~(1<<EN);
_delay_ms(1);

void LCD_Init (void) /* LCD Initialize function */
{
LCD_Command_Dir |= (1<<RS)|(1<<RW)|(1<<EN);
LCD_Data_Dir = 0xFF;

_delay_ms(20);
LCD_Command (0x38);
LCD_Command (0x0C);
LCD_Command (0x06);
LCD_Command (0x01);
LCD_Command (0x80);
}

void LCD_String (char *str)
{
int i;
for(i=0;str[i]!=0;i++)
{
LCD_Char (str[i]);
}
}

void LCD_String_xy (char row, char pos, char *str)
{
if (row == 1)
LCD_Command((pos & 0x0F)|0x80);
else if (row == 2)
LCD_Command((pos & 0x0F)|0xC0);
LCD_String(str);
}
#define Trigger_pin PA0

int TimerOverflow = 0;

ISR(TIMER1_OVF_vect)
{
TimerOverflow++;
}

int main(void)
{
char string[10];
long count;
double distance;

DDRA = 0x01;
PORTB = 0xFF;

LCD_Init();
LCD_String_xy(1, 0, "Ultrasonic");

sei();
TIMSK = (1 << TOIE1);
TCCR1A = 0;

while(1)
{

PORTA |= (1 << Trigger_pin);
_delay_us(10);
PORTA &= (~(1 << Trigger_pin));

TCNT1 = 0;
TCCR1B = 0x41;
TIFR = 1<<ICF1;
TIFR = 1<<TOV1;

while ((TIFR & (1 << ICF1)) == 0);
TCNT1 = 0;
TCCR1B = 0x01;
TIFR = 1<<ICF1;
TIFR = 1<<TOV1;
TimerOverflow = 0;

while ((TIFR & (1 << ICF1)) == 0);
count = ICR1 + (65535 * TimerOverflow);

distance = (double)count / 466.47;

dtostrf(distance, 2, 2, string);
strcat(string, " cm ");
LCD_String_xy(2, 0, "Dist = ");
LCD_String_xy(2, 7, string);
_delay_ms(200);
}
}